Plug Valve Vs. Ball Valve: What are the Differences?

Control valves are an integral part of any production setup that monitors, controls, or manipulates the flow of a fluid medium through numerous pipe sections. Ball valves and plug valves are the two types of control valves. Though they differ in some aspects, both valves are generally used interchangeably in many applications despite some differences in the way they work and their overall structure.

Key Features of Plug Valve and Ball Valve

Control valves are used across a variety of industries, including oil and gas, chemicals, petroleum refining, wastewater treatment, and even food and beverage. Control valve selection is critical to ensuring the safety and efficiency of your systems. It is therefore important to understand their structure, functionalities, and other aspects, such as cost and maintenance.

1. Structure

Plug Valves

A plug valve is characterized by a conical or cylindrical disc that controls fluid flow through a passage that runs sideways within it. The hollow passage aligns with the flow when the valve is open, allowing fluid to flow freely. By rotating the plug 90 degrees, the valve closes and the flow is blocked.

The plug valve is small and simple and is used for cutting, distributing, or changing the flow of media. Plug valves are typically used in medium- or low-pressure, low-temperature settings, although some types may also be used in high-temperature settings.

Gas plug valves come in four different styles, including lubricated, non-lubricated, expandable, and eccentric, besides two-way, three-way, and multi-point port openings.

Ball Valves

Ball valves are modified plug valves with spherical discs and circular bore passageways. There is a hole in the disc called a port. When both ends of the port align with the valve, the valve is open and the medium flows through it. There is no flow when the port lines up with the ends of the valve.

In addition to their compact structure and ease of operation and maintenance, ball valves are suitable for a variety of applications, including water, natural gas, acids, and solvents. Ball valves work well even with harsh media, such as hydrogen peroxide, methane, ethylene, or oxygen. Traditional gas shutoff ball valves are most suitable for open and close functions, but advanced or customized versions can be used for flow control and throttling.

Ball valves come in four different types of construction:

• With full port or full bore ball valves, the hole and pipeline sizes are the same, resulting in lower friction loss. Since the valve is more expensive and larger, it is usually used only where free flow is necessary, such as in pipelines requiring pigging.

• Compared to the valve's pipe size, the ball in a reduced bore ball valve is slightly smaller. As a result, the flow area becomes smaller, increasing the flow velocity.

• The V-port ball valve features a v-shaped ball that enables a more controlled opening and closing of the orifice.

• The ball or disc is supported between the stem and shaft of a trunnion mounted ball valve by additional mechanical anchoring. In applications requiring higher pressure or larger valves, this type of ball valve is useful.

2. Function

With a quick 90-degree turn of the actuator, plug valves and ball valves open and shut. Sealing and shut-off operations are their primary functions. However, the sealing surface of a plug valve is significantly larger than that of a ball valve. In addition to better sealing qualities, this also means greater torque and more effort.

The torque-free operation and lightweight of ball valves make them relatively easier to operate than plug valves. The smaller sealing surface may result in poor sealing performance, but advancements in chemical sealants and seal injections have addressed this issue.

3. Maintenance

For control valves to function effectively, they need to be maintained regularly. Plug valves are relatively easy to maintain because they have a simple design and don't have many moving parts. Additionally, the plug can be removed and cleaned easily, and the valve body can also be cleaned easily.

Ball valves are harder to clean because the ball or disc is located deep inside the valve, making access difficult. Eventually, the ball valve's body cavity may accumulate particles from the medium, which makes cleaning and maintaining it more challenging.

When compared with ball valves, plug valves offer low-cost operations. Due to the fact that the plug fits under the bushing in a plug valve, there is no wear on the valve body or plug. To maintain the valve's optimum function and long-term service requirements, all that needs to be done is to replace the bushing and top seal.

4. Application

Due to their large surface area and unrestricted flow, plug valves are ideal for applications that involve mud, slurries, or sewage. A fortified plug valve provides tight seals even when dealing with hard or corrosive media. Their simple structures, ease of operation and maintenance, and anti-corrosion qualities make them reliable shutoff options for most critical applications.

Among their applications are gas feed lines, crude oil, LNG, field gas or polymer plants, turbines, compressor, separator skids, tank farms, oil refinery feedstock lines, hydrocarbon processing, and more. Stainless steel ball valves are suitable for cooling water, petroleum refining, feed water, brewing, and desalination, while high-pressure ball valves are excellent for underground, subsea, and cryogenic applications.

What Type of Control Valve Should You Use?

The purpose of 2 Way ball valve and plug valves is to offer greater control over the flow of fluid. Because they ensure optimal seals for various industrial applications, they are called control valves. To choose the right valve, it's important to understand the differences and capabilities.

Plug valves rank higher in terms of their tight sealing capabilities, despite being more expensive and heavier. Despite this, they are indeed difficult to operate. Ball valves are the best choice for large applications that require an easier operation. However, keep in mind that their sealing capabilities are not as good as plug valves. Ball valves may need additional technology and updated mechanisms to improve their sealing capabilities.